Lexington Weather

Lexington, Massachusetts, USA

53°F

5/11/2024 12:40pm

Lexington Conditions: Mostly cloudy
Temperature: 53.1°F / 11.7°C
Dew Point: 44.2°F
Relative Humidity: 72%
Wind: Calm, 10-min avg: Calm, gust: 2 mph
Barometer: 29.82 in Steady
Visibility: 10 miles
Rain Today: 0.00 in

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 111055
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
655 AM EDT Sat May 11 2024

.SYNOPSIS...
A ridge of high pressure builds into New England today with dry but 
cool conditions. An upper level low pressure may bring a few hit or 
miss showers Sunday but a mostly dry day with below normal 
temperatures. Milder next week with the risk for showers increasing 
Tuesday into Wednesday, then mainly dry and seasonable toward the 
end of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Mid level trough will be exiting to the east by daybreak while 
upstream trough moves through the Gt Lakes today. Subsidence and 
weak ridging aloft between these 2 systems will result in a mainly 
dry day today. Plenty of sunshine to start the day away from the 
Cape/Islands, but lingering low level moisture and somewhat cooler 
air aloft will result in diurnal cu developing this morning and 
expanding across the region leading to mixed clouds and sun. Can't 
rule out a spot shower this afternoon in western New Eng where steep 
low level lapse rates develop, but otherwise it's a dry day. 850 mb 
temps around 0C today so below normal temps with highs mid ranging 
from mid 50s east coastal MA to low-mid 60s CT valley with E-NE 
flow.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Tonight...

The mid level trough over the Gt Lakes moves east and 
approaches New Eng tonight with cooling temps aloft. Clouds 
will increase ahead of the system and may see a few showers in 
western New Eng late tonight, but otherwise a dry night. Lows 
mostly between 40 and 45. 

Sunday...

The mid level trough and cold pool moves overhead during Sun with 
500 mb temps near -25C. Brunt of shortwave energy will be moving 
from the Gt Lakes to mid Atlc region where best chance for showers. 
This is where moisture and limited instability is greatest. There is 
no instability in SNE and moisture is limited, but cold pool aloft 
will help to generate a few showers, mainly in western New Eng, but 
dry most of the time with mostly cloudy skies. Another cool day with 
850 mb temps 0 to -1C. Highs will be mostly in the mid-upper 50s 
with light winds and sea-breezes developing.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Key Points:

* Warming trend this week with more seasonable highs

* Dry much of Monday and Tuesday

* Next best chance for rain Tuesday night into Wednesday

Monday - Wednesday

Upper level closed low and cold pool finally move out of the region 
to the NE while a weak ridge and high pressure extend north from the 
Mid Atlantic. Some guidance shows low chances for showers late 
Monday into Tuesday especially with warm air advection kicking in. 
However, rising heights and dry mid levels should suppress rain 
activity from becoming more then just an isolated shower. Better 
moisture and forcing doesnt arrive until late Tuesday into Wednesday 
as a decaying shortwave trough and associated surface low exits out 
of the Ohio River Valley and passes just south of the region. Still 
considerable uncertainty with how far north the track of the center 
of low pressure goes with much of the shortwave forcing remaining 
south of the region again. Even if the low stays south of the 
region, thinking there will still be wide spread rain across the 
region as the warm front stalls over the region. PWATS increase to 
1.25-1.5 inches Tuesday night into Wednesday ahead of the shortwave 
trough. Ensemble QPF remains rather spread due to the uncertainty in 
the track of the low. 24 hour LREF 25th-75th percentiles show a 
widespread 0.25-1.0 inches is possible with low probs up to 10% for 
2 inches mainly along the south coast. Not too concerned about 
convection or thunder chances at this time with models keeping 
instability south of the surface low in its warm sector. High temps 
Monday and Tuesday recover into the upper 60s to low 70s, but remain 
more uncertain for Wednesday where temps could range from the upper 
50s to upper 60s depending on how long rainfall lasts into 
Wednesday. 

Thursday and Friday

Upper level ridge and surface high pressure build in behind the 
shortwave which should allow for dry conditions Thursday into Friday. 
There is some considerable differences in the GFS and EURO due to 
the EURO creating a cutoff low just south of the region. This cut 
off could keep the very dry airmass from over southern Canada from 
reaching into SNE. Either way, temps Thursday and Friday look to 
reach the low to mid 70s.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecast Confidence Levels:

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent. 


Today...High confidence.

VFR cigs across the region, but MVFR persists at ACK and HYA.
Stratocumulus will form and may bring brief periods of MVFR 
ceilings as they could form anywhere from 2000-4000ft. E-NE 
winds 10-20 kt, gusts to 25 kt at ACK.

Tonight...Moderate confidence. 

VFR cigs, but MVFR may develop across the CT valley and
Cape/Islands late tonight. Light winds.

Sunday...Moderate confidence. 

Mainly VFR cigs, but areas of MVFR and scattered showers 
possible across western MA/CT. SE wind 5-10 kt with sea breezes
developing. 

KBOS TAF...High confidence in TAF. 

KBDL TAF...High confidence in TAF. 

Outlook /Sunday Night through Wednesday/... 

Sunday Night through Monday: VFR. 

Monday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA.

Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.

Tuesday Night: Mainly MVFR, with areas IFR possible. Breezy.
SHRA likely, isolated TSRA.

Wednesday: MVFR/IFR conditions possible. Breezy. Chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent. 

Through Sunday...

A brief period of 25 kt NE wind gusts possible this morning across 
the SE waters as low pres makes its closest approach to the southern 
waters. Otherwise NE winds 10-20 kt today diminishing and becoming 
light tonight and Mon as weak high pres moves over the waters. Winds 
will become onshore over the nearshore waters Sunday as sea-breezes 
develop. SCA for SE waters through tonight for 25 kt gusts this 
morning and 5 ft seas lingering into tonight.

Outlook /Sunday Night through Wednesday/... 

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. 

Monday: Winds less than 25 kt. Seas locally approaching 5 ft. 

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers. 

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Slight
chance of rain showers. 

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft. Chance of rain
showers. 

Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Seas up to 5 ft. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ254-255.

&&

$$

SYNOPSIS...KJC/KP
NEAR TERM...KJC/KP
SHORT TERM...KJC
LONG TERM...KP
AVIATION...KJC/KP
MARINE...KJC/KP